1. Field of Invention
This invention relates to communication systems, methods and program products. More particularly, this invention relates to automatic and seamless vertical roaming between a wireless local area network (WLAN) and a wireless wide area network (WWAN) while maintaining an active voice or streaming data connection: systems, methods and program products.
2. Description of Prior Art
Wireless personal digital assistants (WPDA) and “smart” cellular telephones are the most popular devices known to provide “mobile Internet” access for the mass consumer market. At this point, no one has yet developed a technology that combines WLAN based Voice over Internet Protocol (VoIP) and streaming DATA with WWAN circuit switched telephony such that the transition between WWAN and WLAN voice connections occur seamlessly and automatically. With such development, WLAN based voice telephony will provide a benefit to carriers that manage both infrastructures to seamlessly and automatically move traffic from overloaded WWAN networks over to higher bandwidth WLAN networks when the subscriber moves. Carriers and network equipment manufacturers that produce both WWAN and WWLAN infrastructure products can now have a mechanism for a successful business and billing model around both WWAN and higher speed WLAN based mobile Internet access. In addition, spillover enterprise and consumer level markets will expand with a domino effect as mobile professionals seek to bring the benefits of their high speed Internet and IP based voice access into their homes and small offices.
Prior art related to automatic voice or data transfer between different wireless networks includes:
(1) U.S. Pat. No. 5,682,379 discloses a transceiver apparatus for creating a wireless personal local area network between a computer terminal and one or more peripheral devices. A separate transceiver is connected to the computer terminal and to each peripheral device. The transceivers can be connected to the terminal or peripheral device either internally or externally. A low power Radio is used to communicate information between the computer terminal and peripheral devices. Different transceivers can be used for modifying the carrier frequency and power of the local area network. The microprocessor is located inside each transceiver and controls the information flow of the transceiver including the communication protocol which allows each device to know if other devices are communicating, which devices are being communicated to, and selectively address the peripheral devices. An Idle Sense communication protocol is used for information transfer between the computer terminal and the peripheral devices, increasing efficiency in power management and compensating for transmission collisions.
(2) U.S. Pat. No. 5,790,527 discloses a trunked Radio communications system, apparatus and methods for transparently updating existing frequency division multiple access (FDMA) communications facilities to accommodate time division multiple access (TDMA) communications. TDMA channels are added to existing FDMA sites on an individual basis to increase spectral efficiency and capacity while still being compatible with existing FDMA equipment and protocols. For example, the existing FDMA control channel and protocols are used by dual mode sites and dual mode Radios. A dual mode Radio transceiver selectively participates in trunked Radio communications in either an FDMA mode or in a TDMA mode. Each dual mode Radio includes a memory for storing a mode identifier identifying each channel as an FDMA or a TDMA working channel. When a channel assignment is made, the dual mode Radio determines from that channel mode identifier stored in memory whether to operate in the FDMA or TDMA mode for that particular communication. Moreover, dual mode Radios expedite synchronization to a TDMA working channel (time slot) using a timing relationship established between the FDMA control channel and the TDMA working channels. In the context of multiple site, trunked Radio communications, the present invention provides for interoperability between sites and Radios which have TDMA communications capabilities and sites and Radios which have only FDMA capabilities.
(3) U.S. Pat. No. 6,075,985 discloses a fixed wireless access system includes a base station for bi-directional communication with a switching center, a private branch exchange (PBX) for bi-directional communication with a plurality of user stations, and a wireless trunk interface (WTI). The WTI communicates with the base station over a bi-directional wireless air link and with the PBX over a bi-directional trunk line. Since a wireless link is established between a dual Radio unit (DRU) at the base station and a transceiver at the WTI, the slots normally allocated to the directory number of the called and calling parties in the current air interface, must be used to identify the transceiver involved in the exchange of information. Therefore, the DN of the called station behind the PBX is transmitted to the WTI using other fields of the air interface, and presented to PBX in a format acceptable for establishing a correct connection (DID service). Similarly, the DN of the calling station behind the PBX, is transmitted to base station and presented to switching center using a format acceptable for use by the switching center (AIOD service).
None of the prior art discloses automatic and seamless vertical roaming between a WLAN and a WWAN by detecting second network availability for switching over while maintaining an active voice or data connection on the first network so that the existing connection is maintained and the transition is continuous.